1

Supplemental Data

for

Emissions Characterization of Outdoor Wood-Fired Hydronic Heater Technologies

John S. Kinsey, Abderrahmane Touati, Tiffany L. B. Yelverton, Johanna Aurell, Seung-Hyun Cho, William P. 

Linak, and Brian K. Gullett

S-1. Appliance and fuel specifications

As discussed in the main text, four different models of residential wood-fired hydronic heaters (RWHHs) 

were tested in the program. Single- to triple-staged units, in updraft and downdraft combustion configurations, and 

using logs/split log cordwood and pellets as fuel, were tested. Basic specifications for each unit are provided in 

Table S-1 with photos and schematics shown in Fig. S-1. 

Three basic wood fuels were also tested. Analyses of these test fuels are shown in Table S-2.

Table S-1

Specifications of appliances tested.a

Appliance A B C D

Technology Single-stage 

combustion

Three-stage 

combustion

Two-stage combustion Two-stage 

combustion and 

gasification with heat 

storage

Fuel Cordwood Cordwood Hardwood pellets Cordwood

Heat capacity, 

maximum output -

kW (103 BTU h-1)

38b

(131)

50

b

(172)

40

(137)

44

(150)

Water capacity-liters 740 1700 160 120

a As supplied by the manufacturer unless otherwise specified.

b Value based on maximum capacity from certification testing using EPA Method 28 OWHH (OMNI, 2007; OMNI, 

2008; USEPA, 2012).

Table S-2

Ultimate and proximate fuel analyses.

Properties Test methoda Red oak Pine Pellets

Higher heating value 

(kJ/kg)

Calculation from fuel 

analysis

19510 21570 19830

Ash (%) ASTM D3174-07 1.46 0.44 0.52

Loss on drying 

(LOD)

GLI Procedure S-200 22.52 9.68 7.24

Volatile matter (%) ASTM D3175-07 84.23 88.50 84.27

Fixed carbon (%) Calculation 14.31 11.06 14.11

Carbon (%) GLI Procedure ME-2 48.70 51.72 50.10

Chlorine (ppm) GLI Procedure ME-4A 38 36 44

Hydrogen (%) GLI Procedure ME-2 5.96 6.57 5.86

Nitrogen (%) GLI Procedure ME-2 <0.5 <0.5 <0.5 

Sulfur (%) GLI Procedure E 16-2 <0.05 <0.05 <0.5

a ASTM = ASTM International; GLI = Galbraith Laboratories, Inc., Knoxville, TN.
2

Fig. S-1. Photos and diagrams of the appliances tested in the study.

Appliance A Appliance B

Appliance C Appliance D
3

1 In certain tests, 4.5 % by weight of mixed refuse was fired with red oak cordwood to simulate situations in 

2 which residential waste is co-fired for ignition or disposal purposes. The mixed refuse was constructed by hand3 selection of components, weighing, and division into individual charges to assure consistency between tests.

4 S.2 Experimental apparatus

5 The experimental apparatus for the study is illustrated in Fig. S-2. Measurements were conducted either 

6 outdoors or indoors depending on the parameter being measured. In addition, appropriate temperature and flow data 

7 were collected on the heated water recirculated to and from the appliance as well as the water-to-water heat 

8 exchanger connected to the building chilled water supply. For Appliance D, an additional water-to-air heat 

9 exchanger was added in series with the water/water heat exchanger used for the other units. See details in the main 

10 text.

11 Fig. S-2. Schematic of experimental apparatus used in the study.

12 S-3. Heat demand control system

13

14 The heat load demand was simulated by extracting the RWHH outlet heat with a water/water heat exchanger 

15 coupled to the building chilled water supply (Fig. S-2). The RWHH units were operated in a mode where hot water 

16 was continuously circulated through the water/water heat exchanger and the unit’s water jacket. The water flow

17 system consists of two 25 mm outside diameter, oxygen barrier lines insulated with high density urethane. The same 

18 plumbing system was used for all four units tested. The inlet and outlet temperatures of both the chilled water and 

19 re-circulated hot water were monitored, as well as the chilled water flow rate. The heat load demand control system 

20 determined the change between the chilled water outlet temperature and the chilled water inlet of the heat 

21 exchanger. The system controlled the heat removal by adjusting the chilled water flow rate through the use of the 

22 proportional valve. The heat load demand control scheme is shown in Fig. S-3.
4

23

24 Fig. S-3. Diagram of heat demand control system.

25 S-4. Heat load profile

26 As discussed in the main text, the heat load profile (Fig. S-4) that was used throughout the testing program was 

derived from the Energy-10TM 27 simulation program for heat demand developed by the U. S. National Renewable 

Energy Laboratory for a 232 m2 28 home located in Syracuse, New York. In this simulation, an averaged hour-per29 hour heat load for the first 2 weeks of January as determined over a period of the last 25 years (courtesy of 

30 Brookhaven National Laboratory) was used. The average daily heat load for the first two weeks in January is about 

31 827 MJ. 

32 Fig. S-4. Heat load profile used in all RWHH tests.

Proportional 

Valve

Flow 

meter

Data Acquisition

System

Heat Exchanger

OWHH Outlet Water

Temperature

OWHH Inlet Water

Temperature

Thermocouple

Proportional Thermocouple

Valve

Flow 

meter

Data Acquisition

System

Heat Exchanger

OWHH Outlet Water

Temperature

OWHH Inlet Water

Temperature

Heat Exchanger

OWHH Outlet Water

Temperature

OWHH Inlet Water

Temperature

Thermocouple

Thermocouple

0

2

4

6

8

10

12

14

266

267

267

268

268

269

269

270

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

HeatLoad (kW)

A

mbientTemperature (

oK)

Time of Day (Hours)

Temperature

Heat Load
5

33 S-5. Detailed experimental results

34 The specific experimental data used to generate Fig. 2, Fig. 3, and Fig. 5 of the main text is shown in Tables 

35 S-3, S-4, and S-5, respectively. Also shown in these tables is the 1σ error associated with each average value. 

36 Additional information can also be found in the final report for the study (Gullett et al., 2012). Table S-6 also 

37 provides the detailed chemical composition of the particles generated by Appliances A, B, and C.

38 Table S-3.

Thermal performance data.a39

Appliance and fuel type Thermal 

efficiency (%)

Boiler 

efficiency (%)

Combustion 

efficiency (%)

Appliance A-Oak 22 + 5.0 NA 74 + 3.0

Appliance A-Oak+Refuse 31 + 2.2 NA 87 + 3.4

Appliance A-Pine 29 + 1.8 NA 82 + 3.2

Appliance B-Oak 30 + 3.2 NA 86 + 1.8

Appliance C-Pellets 44 + 4.1 86 + 3.5 98 + 0.16

Appliance D-Oak NA 83 + 0.71 90 + 0.79

a

40 NA = not available.

41

42 Table S-4.

Emission factors for gas-phase air pollutants.a43

Appliance and 

fuel type

Carbon dioxide 

(g kg-1dry fuel)

Carbon monoxide 

(g kg-1dry fuel)

Total hydrocarbons 

(g kg-1dry fuel)

Nitrous oxide (mg 

kg-1dry fuel)

Appliance AOak1330 + 33.5 193 + 17.0 54.3 + 20.7 36.6 + 4.80

Appliance AOak + Refuse1500 + 41.5 158 + 25.3 13.2 + 5.41 18.2 + 5.66

Appliance APine1530 + 176 189 + 39.0 33.6 6.35 + 1.76

Appliance BOak1560 + 37.0 117 + 17.4 15.0 + 4.01 NA

Appliance CPellets1820 + 1.47 8.3 + 3.40 0.554 + 0.445 123

Appliance DOak1520 + 77.0 140 + 37.0 14.2 + 4.34 59.6

a

44 NA = not available.

45 Table S-5.

46 Emission factors for particle-phase air pollutants.

Appliance and fuel type Total PM mass 

(g kg-1dry fuel)

Total PM number 

(particles kg-1dry fuel)

Appliance A-Oak 24.8 + 2.05 1.44 x 1014 + 3.76 x 1013

Appliance A-Oak+Refuse 24.3 + 2.96 1.07 x 1014 + 5.42 x 1013

Appliance A-Pine 46.9 + 6.02 2.39 x 1014 + 1.60 x 1014

Appliance B-Oak 4.55 + 2.47 4.61 x 1013 + 4.45 x 1013

Appliance C-Pellets 0.312 + 0.183 8.50 x 1010

Appliance D-Oak 3.30 + 0.680 9.62 x 1013 + 8.27 x 1013

47
6

48 Table S-6.

49 Inorganic and organic particle composition.

50

Element

Mass fractionb

Appliance A Appliance B Appliance C

K 0.00242 0.0279 0.140

Na 0.000107 0.00110 0.00551

Si 0.000173 0.00275 0.00219

S 0.000147 0.00501 0.0423

Cl 0.000319 0.00648 0.0192

Ca 0 0 0.00231

Fe 0.000632 0.0381 0.0323

Cu 0.000688 0.0288 0.0249

Zn 0.0000776 0 0.00719

P 0 0 0.000482

O

a

0.00133 0.0377 0.0986

Total ash 0.00589 0.148 0.375

Organic carbon 0.925 0.801 0.250

Elemental carbon 0.0696 0.0511 0.375

a

51 Assumes oxides.

b

52 Three significant figures.

53

54 S-6. Supplemental data references

55

56 Gullett,B., Dodder, R., Gilmour, I., Hays, M., Kinsey, J., Linak, W., Loughlin, D., Oudejans, L., Yelverton, T., 

57 2012. Environmental, Energy Market, and Health Characterization of Wood-Fired Hydronic Heater Technologies. 

58 Report No. 12-15, New York State Energy Research and Development Authority, Albany, NY.

59

60 OMNI-Test Laboratories, 2008. Certification Test Report, Central Boiler, Inc., Wood-Fired Hydronic Heater. Report 

61 No. 072-O-04-3, Beaverton, OR, July.

62

63 OMNI-Test Laboratories, 2007. Certification Test Report, Central Boiler, Inc., Wood-Fired Hydronic Heater. Report 

64 No. 117-O-23-3, Beaverton, OR, December.

65

66 USEPA, 2012. Test Method 28 OWHH for Measurement of Particulate Emissions and Heating Efficiency of 

67 Outdoor Wood-Fired Hydronic Heating Appliances. U. S. Environmental Protection Agency, Office of Air Quality 

68 Planning and Standards, Research Triangle Park, NC. http://www.epa.gov/ttn/emc/prelim/otm15.pdf (accessed 

69 24.08.12).

70